Water activities are one of leisure activities that people loves to do, such as swimming, surfing or driving sails. The most worrying thing about water activities is the safety. When someone falls into the water and waits for rescue, if there is no ideal auxiliary life-saving equipment, the drowning person may be in a state of exhaustion even if he/she has skills in swimming. Therefore, it is necessary to wear a life jacket for water sports. A common life jacket having Styrofoam is inconvenient for surfing activities due to the internal Styrofoam material. In recent years, a life jacket is developed, which has a built-in air bag and a compressed air cylinder. In normal use, the air bag is not inflated, so the life jacket is thin and won't impede human activities. Once the user falls into the water and waits for rescue, the compressed air in the air cylinder can be poured into the air bag to provide buoyancy so that the user is buoyant on water. However, if the air bag is broken by a reef, a rock or the like, this kind of life jacket will decrease or loss buoyancy to cause a danger.
Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve these problems.